Use of cocaine has been linked to increased risk of child abuse and neglect. Research in rats by Johns et al. (1) has shown that cocaine exposure during pregnancy decreases maternal behavior while enhancing aggression, effects linked to decreased activity of oxytocin (OT), a neuropeptide known to enhance maternal behavior and bonding. Light et al. (2) showed that mothers with prenatal exposure to cocaine tend to hold their babies less often at home, have greater stress and negative affect based on physiological and selfreport measures, and show lower OT levels before and after baby holding than mothers with no substance exposure. Thus, we hypothesize that: 1. decreased maternal OT activity, greater maternal stress and negative affect, and fewer and poorer quality mother-infant interactions are consequences of prenatal cocaine; 2. in addition to cocaine's effects on the mother, these outcomes may be related to differences in the infant's signals (cries, behavior during social interaction). The present investigation will examine these translational neurobehavioral patterns by studying 180 mother-infant dyads at 1 month postpartum, including 75 with prenatal cocaine exposure, 30 with prenatal drug exposure other than cocaine, and 75 non-exposed dyads. Infants will undergo MRI to assess maturation of brain structures. Acoustice analysis of their cry characteristics which might influence maternal response will be performed. Mothers will undergo 24-hour home monitoring of their mood, stress, and frequency of baby holding using diary data recorded 4 times per hour together with ambulatory blood pressure (BP) and heart rate (HR). Maternal plasma OT, vasopressin (VP), prolactin, stress hormones and mood ratings, along with BP and HR variability, will also be assessed during multiple lab events designed to elicit maternal biobehavioral responses: 1. mother-infant face-to-face interaction (videotaped for blinded ratings of maternal touch, co-regulation /mutuality, and emotional quality); 2. brief (8 min) mother-infant separation followed by reunion; 3. a speech stressor; 4. listening to and rating tape-recorded infant cries that vary in frequency and temporal characteristics; 5. viewing photos of babies in safe and happy vs. unhappy or dangerous contexts. Maternal ratings of positive and negative affect to these events will be examined and related to physiological responses. In a pilot feasibility component, mother and infant salivary and urinary measures (OT, VP, alpha-amylase and cortisol) will also be obtained. This research will provide insights into the effect of prenatal exposure to cocaine on the quality of the motherinfant relationship and neurobehavioral pathways influencing maternal stress, affect and behavior, which may have profound implications for the health and well-being of both mother and child.